Field of the Disclosure
The disclosure relates to a closure for a product retaining container. Moreover, the disclosure relates to a use of a closure for closing a product retaining container and to a method of manufacturing said closure. The disclosure also relates to a closure system and a method for controlling and/or changing the gas composition and/or pressure within the head-space of product-retaining container and the use of a closure therein.
Technical Background
In view of the wide variety of products that are dispensed from containers, numerous constructions have evolved for container closures, including, for example, screw caps, stoppers, corks and crown caps, or the like. Generally, products such as vinegar, vegetable oils, laboratory liquids, detergents, honey, condiments, spices, alcoholic beverages, and the like, impose similar requirements on the type and construction of the closure means used for containers for these products. However, wine sold in bottles represents the most demanding product in terms of bottle closure technology, due to the numerous and burdensome requirements placed upon the closures used for wine bottles. In an attempt to best meet these demands, most wine bottle closures or stoppers have historically been produced from a natural material known as “cork”.
While natural cork still remains a dominant material for wine closures, synthetic wine closures have become increasingly popular over the last years, largely due to the shortage in high quality natural cork material and the problem of wine spoilage as a result of “cork taint”, a phenomenon that is associated with natural cork materials. In addition, synthetic closures have the advantage that by means of closure technology, their material content and physical characteristics can be designed, controlled and fine-tuned to satisfy the varying demands that the wide range of different wine types produced throughout the world impose on closures.
In closure technology, oxygen management is one of the most critical features. Oxygen is a key reactant that causes a sensory change in wine in its package. Moreover, oxygen is a major determinant of shelf life. In selecting an optimal closure for a particular type of wine, one has to strike a delicate balance between tightly sealing the bottle content to prevent leakage, avoid contaminants, counteract degradation and spoilage by oxidation, on the one hand, and, on the other hand, permitting a restricted amount of oxygen to enter the container, so as to ensure full maturation of the wine flavor characteristics and prevent the formation of unpleasant aromas. Recent scientific studies appear to confirm what has already been accepted empirical knowledge in the traditional art of winemaking: that oxygen is intimately involved in the aging and maturation process of bottled wine.
If certain types of wines are completely starved of oxygen for longer periods of time, a process known as reduction may give rise to malodorous sulfur compounds such as certain sulphides (sulfides), thiols and mercaptans. To prevent reduction over the entire period of wine aging and maturation, a minute but constant concentration of oxygen within the container interior is believed to be necessary. The olfactory defect occurring otherwise is sometimes referred to as reduced character and can be readily identified by the presence of odors reminiscent of rotten egg, garlic, stagnant water, burnt rubber, struck matches and/or cooked cabbage. Even at low concentrations, these odors may completely ruin a wine's character.
On the other hand, wines that are to be consumed young, such as most types of white wines, must be protected from oxygen as ingress of oxygen impairs the fresh and fruity appeal of these wines. However, also for other wines, marked oxidation has an adverse effect on wine quality.
Hence, there is a need for advanced bottling technology and superior closure types which allow winemakers to choose and exactly control the amount of oxygen that a wine is exposed to during bottling and bottle aging.
In bottled wine, the total oxygen present in the bottle (total package oxygen, TPO) is generally thought of as the sum of dissolved oxygen and the oxygen present in the air of the headspace (i.e. the ullage volume between fill level and closure), both of which can be derived from several sources. First, contact of the wine with air during bottle filling, can result in an increased amount of dissolved oxygen in the wine. Secondly, gaseous oxygen trapped in the bottle headspace after bottling and bottle closure is another major source of oxygen. The amount of oxygen present in the headspace can vary, depending on headspace volume, which is determined by bottle dimensions, fill level, and/or bottle neck space that is occupied by the closure, as well as the oxygen concentration in the gas phase occupying the head space. The amount of oxygen present in the gas phase after bottling can be reduced, for example, by applying headspace management technology such as, for example, evacuation (vacuum) or inerting (e.g. flushing with carbon dioxide or nitrogen) the headspace immediately before the bottle is closed. Thirdly, after bottling and during storage, oxygen ingress through the closure, as determined by the oxygen transfer rate (OTR) of the closure, may be responsible for additional oxygen uptake.
Finally, besides these three aforementioned routes of oxygen uptake, it has been found that immediately after closing wine bottles with natural or synthetic cork stoppers, off-gassing of air from the compressed cork material may further contribute to an initially high local oxygen concentration in the bottle headspace. Such off-gassing of the closure may be caused by the compression which the closure undergoes when being inserted into the bottleneck. The compression may lead to diffusion of air present in the cork in all directions possible, including into the bottle headspace. The ratio of air being forced into the bottle headspace compared to the proportion moving outside of the bottle will be determined inter alia by the pressure under the closure, with greater transfer into the headspace at more negative headspace pressures.
The off-gassing phenomenon, which has also been referred to as “desorption” of the closure (Dieval, J.-B. et al., Packag. Technolog. Sci. 2011 and references therein), becomes evident from curves depicting the oxygen ingression kinetics after bottle closure. Without wishing to be bound by theory such curves can generally be divided into two parts. In a first phase, there is a relatively fast and non-linear oxygen ingress into the bottle headspace. Later-on, in a second phase, which typically begins a couple of weeks to a year after bottling and lasts for the years of subsequent storage, the oxygen ingress rate is slower but constant and follows a linear curve, the slope of which is defined by the respective closure's OTR. The first faster and non-linear oxygen ingress is generally caused by the off-gassing of air, which was present in the closure and is forced out of the closure by the compression of the closure in the bottle neck after bottling. The second phase generally is the oxygen that diffuses from the outside atmosphere through the closure and into the bottle headspace. In the following, the gas ingress from within the closure, i.e. the first phase, will be referred to as closure desorption. This is used within the present disclosure synonymous to other suited terms such as off-gassing, outgassing of the closure or ingress of oxygen from within the closure itself upon closing. In particular, the use of the term desorption shall not limit the present disclosure to the physical phenomenon scientifically described as desorption. The term desorption as used in the description of the present disclosure is rather meant to include any release of a gas from the closure itself, which, by way of example, was trapped in the closure, e.g. in voids or cells present in the closure, or dissolved, adsorbed, chemically or otherwise bonded to the closure material and which is released into the interior of the container upon or after closing the container with said closure.
Advances in headspace management technology such as evacuation or inerting (e.g. flushing with nitrogen) the headspace before closing bottles have made it possible to minimize the starting amount of oxygen present in wine bottles after bottling. Though simple in principle, applying headspace management technology incurs additional costs for the wine maker. On the other hand, advances in (synthetic) closure technology have made it possible that winemakers today can select from a variety of different synthetic closures the optimal closure with an OTR, best-suited for their individual winemaking needs. However, to date there are no means to eliminate, control or change the amount of air and therefore oxygen that enters the closed container through closure desorption, the impact of which on wine aging, sensory properties and quality is only begun to be fully understood. The potentially high amount of oxygen initially entering the bottle through closure desorption, however, can lead to adverse effects and uncontrolled oxidation. There is a need for closures with a defined and controllable amount of oxygen being supplied to the bottle content. Thus, next to controlling closure OTR, there is a need for closure technology that allows control of closure desorption.